The immunology and biochemistry of renal glomerular antigens will be investigated in order to further define the biochemical nature of the glomerular lesions of diabetic nephropathy. Furthermore the role of these antigens, and antibodies reacting with these antigens, in the evolution of diabetic microvascular disease will be studied. The role of the immune system in the development of diabetic renal-retinal disease remains poorly understood and the research plan of this proposal attempts to address this question. We have produced monoclonal antibodies which react with shared antigens of pancreatic islets, renal glomeruli, and retinal pericytes. We have used on antibody (3G5), an IgM, to selectively enrich retinal capillary pericytes in culture by fluorescence activated cell sorting, and we have characterized the pericyte antigen as being a ganglioside by immunostaining of glycolipids separated by thin layer chromatography (TLC). We have found that a ganglioside of similar mobility is the target antigen of 3G5 in pancreatic islets, but the glomerular antigen has not yet been characterized. Additionally, preliminary studies indicate that islet cell autoantibody containing sera of Type I diabetics may also react with renal glomeruli, suggesting a possible immunopathogenetic role for cross reactive antibodies and/or shared antigens. It is, therefore, proposed to screen a large panel of monoclonal antibodies to islet cells for cross reaction with renal glomeruli and/or retinal pericytes, and the monoclonal antibody defined antigens will be biochemically characterized. Biochemical characterization of relevant antigens will be performed using the following approaches: radiolabeling of antigens and TLC or electrophoretic chromatography, HPLC, and affinity chromatography. Additionally, a bank of frozen sera from Type I diabetics will be screened for antiglomerular autoantibodies, and the pattern of binding of monoclonal antibodies and diabetic autoantibodies to normal and diabetic kidney will be ascertained. Finally, the ability of monoclonal antibodies and diabetic autoantibodies to induce mesangial cell proliferation and synthesis of extracellular matrix components and growth factors in vitro will be evaluated as a possible mechanism for the evolution of mesangial expansion in diabetic nephropathy and proliferative lesions of diabetic retinopathy. This will involve 3H-thymidine incorporation studies of proliferation, and the measurement of synthetic activity by northern blot, radioimmunoassay, and radioreceptor assays.